An optical transceiver generally implements an OSA that performs conversion between an electrical signal and an optical signal, and an electronic circuit for processing the electrical signal. FIGS. 11A and 11B show an example of the OSA 201 that provides an optical device 202 and a coupling unit 203. The former element 202 may include a semiconductor laser diode (hereafter denoted as LD), in a case of a transmitter optical sub-assembly (TOSA), for converting the electrical signal to the optical signal. The LD is installed within a housing 202a made of multi-layered ceramics having a plurality of electrodes 202b to transmit signals therein or to provide electrical power thereto. Those electrodes 202b are connected to the circuit board via the flexible printed circuit (hereafter denoted as FPC) 210.
The FPC 210 is connected with the optical device 202 as shown in FIG. 11B. Specifically, facing the pads of the FPC against the bottom surface of the ceramic package 202a and bending the FPC at a portion 211 neighbor to the pads, those pads are soldered with the electrodes of the package 202a. Solder to fix the pads on the FPC 210 to the electrodes of the package 202a creeps up to the side portion of the package 202a, which is often called as a castellation, to from a solder fillet F. A conventional assembly of the FPC 210 and the optical device 202 may reinforce a portion of the solder fillet F by a support.
The FPC 210 is to be bent at a vicinity of the optical device 202 to be in contact with the circuit board placed behind the optical device 202. However, because of the support 220 or the solder fillet F, an excess length of the FPC 210 is necessary just beside of the package 202a of the optical device 202. This excess length sometimes becomes 1.5 mm or more, which means that the optical transceiver installing the OSA 201 is necessary to provide a room to receive the excess length of the FPC 210, and becomes hard to make the housing thereof small.